Many kinds of medical devices made of rigid plastic such as, e.g. oxygenators and hard-shell venous reservoirs, use connectors molded into the body of the device to allow plastic tubing to be connected thereto. In oxygenator heat exchangers, for example, water connectors have an annular groove near their end, while oxygen connectors have annular barbs for holding tubing on the connector.
When such devices are packaged for shipment and sterilized, the connectors are closed off by sliding dust caps onto them. Conventionally, these are cylindrical devices, closed at one end, made of a soft, pliable plastic material such as plastisol (i.e. polyvinyl chloride with plasticizer) or, more expensively, polyolefin.
A significant problem with the prior art caps arises out of the fact that they rely on the elasticity of the cap material to hold them on the connector. The tolerances of the plastisol material (+1.5 to 0.8 mm) make it difficult to design an adequate and consistent tight fit of the cap onto the port, causing caps to sometimes fall off in shipment. Conversely, the plasticizer in the plastisol migrates out of the cap onto the connector with time and, with a tight fit, can eventually form a bond that makes the cap difficult to remove. Finally, from a manufacturing point of view, conventional caps are undesirable because an installer cannot readily tell if a cap has been pushed far enough onto a connector.